CHAPTER 3 The Molecules of Life

State Standards Standard 1.h. – Most macromolecules in cells and organisms are synthesized from a small collection of simple precursors. Standard 5.a. – Students know the general structures and functions of DNA, RNA, and protein. Standard 4.e. – Proteins can differ from one another in the number and sequence of amino acids.

Organic Molecules A cell is mostly water. The rest of the cell consists mostly of carbon-based molecules –organic compounds . Over 2 million organic compounds known. Life’s diversity results from the variety of organic compounds in cells. Organic chemistry is the study of carbon compounds.

Carbon Chemistry Carbon is a versatile atom. It has four electrons in an outer shell that holds eight. Carbon can share its electrons with other atoms to form up to four covalent bonds. Carbon can use its bonds to Attach to other carbons. Form an endless diversity of carbon skeletons.

The simplest organic compounds are hydrocarbons. These are organic molecules containing only carbon and hydrogen atoms. Composed of a carbon skeleton with hydrogens attached to the carbons.

The simplest hydrocarbon is methane. Figure 3.3

Larger hydrocarbons Are the main molecules in the gasoline we burn in our cars. The hydrocarbons of fat molecules provide energy for our bodies.

The functional groups of an organic compound participate in chemical reactions

Giant Molecules from Smaller Building Blocks On a molecular scale, many of life’s molecules are gigantic. Biologists call them macromolecules. Examples: DNA, carbohydrates Most macromolecules are polymers. Polymers are made by stringing together many smaller molecules called monomers. A huge number of different polymers can be made from a small number of monomers.

Cells link monomers to form polymers by dehydration synthesis http://www.bcconline.com/biol10rs/Pearson-Animations/monomers_and_polymers.swf Figure 3.6a

Polymers are broken down to monomers by the reverse process, hydrolysis Figure 3.6b

dehydration synthesis or hydrolysis. Connects monomers to form a polymer. Produces water as a by-product. Breaks up polymers, forming monomers. Water is used to break bonds between monomers. Joins amino acids to form a protein. Glycerol and fatty acids combine to form a fat. Occurs when polysaccharides are digested to form monosaccharides. -H and –OH groups form water. Nucleic acid breaks up to form nucleotides. Water breaks up.

Includes 4 important types of Biological molecules monomer monomer monomer monomer monomer

Carbohydrates Carbohydrates include: Simple sugar molecules such as glucose in sports drinks Large polysaccharides such as starch molecules in pasta and potatoes

Carbohydrates Functions include: monomers of carbohydrates are the monosaccharides (simple sugars) Monosaccharides are simple sugars. Glucose is found in sports drinks. Fructose is found in fruit. Functions include: Are the fuels for cellular work Their carbon skeleton is used to produce other organic compounds

Carbohydrates The monosaccharides glucose and fructose are isomers. They have the same formula, but their atoms are arranged differently How are these two molecules the same? How are they different?.

Carbohydrates : Disaccharides A disaccharide is a double sugar. It is constructed from two monosaccharides. Examples include: sucrose, lactose, maltose Maltose

Carbohydrates: Polysaccharides Long chains of monosaccharides linked together by dehydration synthesis form polysaccharides (complex carbohydrates). Examples include: starch, glycogen, cellulose Starch Function: PLANTS store sugar to be used later as source of energy or building material Glycogen Function: ANIMALS store sugar to be used later as source of energy or building material Cellulose Function: Building material to form plant bodies

Low-Carb Diets In recent years, “low-carb diets” have become popular. Why could this be a problem?

Organic Molecules Table Macromolecules (polymers) Building Blocks (monomer subunits) Example  Function Carbohydrates (polysaccharides) Monosaccharides Glucose (a monosaccharide)  Energy source for all organisms’ cells Sucrose (a disaccharide)  sweetener used in cooking (extracted from sugar beets) starch (a polysaccharide)  Main energy storage in plants Cellulose (a polysaccharide)  plant building material glycogen (a polysaccharide)  Main energy storage in animals

Lipids Lipids are composed largely of carbon and hydrogen Black = carbon Grey = hydrogen Lipids are composed largely of carbon and hydrogen They are grouped together because they are hydrophobic.

Lipids Black = carbon Grey = hydrogen Examples (functions): Fats/oils (energy storage) In humans … Energy storage Cushioning Insulation Steroids/hormones Cholesterol (stabilizes cell membrane) Hormones (act as chemical messengers that regulation key body processes) phospholipids of cell membrane (regulation in and out of cell) waxes (water protection)

Lipids: Fats Fats are lipids whose main function is energy storage They are also called triglycerides triglyceride “monomers” are glycerol and three fatty acids.

Lipids Triglycerides Animal Fats Plant Oils Saturated (Fully hydrogenated) Unsaturated (one or more double bond not fully hydrogenated) Solid at Room Temp. Liquid at Room Temp Saturated fatty acid tail Not all fats are unhealthy. Example: omega-3 fats found in some fish and nuts Reduce risk of heart disease Relieve arthritis symptoms Reduce IBS (irritable bowel syndrome) Double bond in an unsaturated fatty acid tail Figure 3.15b

Organic Molecules Table Macromolecules (polymers) Building Blocks (monomer subunits) Example  Function Lipids Glycerol and __________ *Unsaturated fat --Oil  *Saturated fat – “Fat”  Steroids hormones 

Proteins Proteins perform most of the tasks the body needs to function. The book describes 10 different types of proteins including… Enzyme protein

Proteins -- The Monomers: Amino Acids Your body has tens of thousands of different kinds of protein. The monomers of proteins are the amino acids There are 20 different amino acids Bonded together like a string of beads The diversity of proteins is because of amino acid order number of amino acids in the polypeptide chain(s)

Protein – monomers: amino acids Each amino acid consists of A central carbon atom bonded to four covalent partners. A side group that is variable among all 20 Each amino acid has specific properties. Amino group Carboxyl (acid) group Serine (Ser) Cysteine (Cys) Leucine (Leu) HYDROPHOBIC HYDROPHILIC

Cells link amino acids together by dehydration reactions. Proteins as Polymers Cells link amino acids together by dehydration reactions. Peptide Bond (covalent bond between 2 amino acids in a dipetide/ polypeptide chain) Amino acid 1 Amino acid 2

Protein Structure

Protein structure A slight change in the primary structure of a protein affects its ability to function. The substitution of one amino acid for another in hemoglobin causes sickle-cell disease.

What Determines Protein Structure? A protein’s shape is sensitive to the surrounding environment. Protein structures can be unraveled and lose their shape because of unfavorable temperature pH changes Salt concentration changes This is called denaturation. H+ By acid

Organic Molecules Table Macromolecules (polymers) Building Blocks (monomer subunits) Example  Function Protein (is made of one or more polypeptide chains*) Structural proteins enzymes  antibodies List at least one more type of protein and its function!!!

Proteins Review What are 3 functions of proteins? What are the building blocks of proteins? Show how 2 of these building blocks can join together? a. What is the name of this reaction? How do proteins differ from one another? What is the primary structure of proteins? a. How do changes in the primary structure affect a protein? 6. What is denaturation and why does this affect the function of a protein?

Nucleic Acids Nucleic acids are information storage molecules. They provide the directions for building proteins. They ultimately control the life of a cell. There are two types of nucleic acids: DNA, deoxyribonucleic acid RNA, ribonucleic acid

Nucleotides The monomers of nucleic acids are nucleotides. Each nucleotide monomer is composed of a sugar, Phosphate nitrogenous base.

RNA v. DNA. RNA nucleotides RNA polynucleotide Its sugar has an extra OH group. It has the base uracil (U) instead of thymine (T). RNA polynucleotide Single stranded A special RNA: ATP (p76-77) ADP +P Energy in ATP ATP  ADP + P + Energy out Cellular respiration: chemical energy harvested from food molecules RNA nucleotide ↑ The sugar phosphate backbone holds the polynucleotide together 

Organic Molecules Table Macromolecules (polymers) Building Blocks (monomer subunits) Example  Function Nucleic Acids ? DNA (nucleic acid)  RNA (nucleic acid) ATP (nucleotide)

Evolution Connection: DNA and Proteins as Evolutionary Tape Measures Evolutionary relationships between organisms can be assessed. Biologists use molecular analysis of DNA and protein sequences for testing evolutionary hypotheses about the relationships between organisms. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings